The present invention relates to a navigation device and more particularly to a device for first establishing the position of a missile in range and cross-track coordinates relative to the position of a target and, after making a heading correction, to provide map guidance means for directing the missile to the target.
Many of the early air-to-ground missiles were carried by a plane to a target area for launching as these early types of missiles had no homing features. One of the main disadvantages of this method of firing missiles is that the delivering aircraft was subjected to continual gun fire as the aircraft entered or neared the target area. In order to relieve this danger to pilots and their aircraft, various devices and systems have been employed to provide automatic guidance so that a missile can home on a target.
One such guidance system is shown and described in U. S. Pat. No. 3,071,765, entitled, "Radar Map Guidance System", which issued Jan. 1, 1963, to Gerald C. Schutz. In this patent, a system is disclosed whereby a reconnaissance airplane is caused to leave a launching platform and separately from a forwardly directed antenna assembly and from a laterally directed radar assembly to make a time track and an azimuth track on preferably a single film that is continuously uninterrupted from the time the reconnaissance aircraft leaves its launching platform until it arrives at a proposed target. The system contemplates an equipment for making the flight record map in the reconnaissance plane and interpreting that record in a pilotless aircraft controlled in azimuth and in time by the two tracks on the film made in the pilotless aircraft for the purpose of causing the pilotless aircraft to duplicate the flight of the reconnaissance aircraft.
Another guidance system is shown and described in U. S. Pat. No. 3,163,377, entitled "Map Matching Navigation Control System For Aircraft", which issued Dec. 29, 1964, to Richard L. Burtner. This patent was concerned with indicating or controlling the flight path of aircraft over areas where large land-water boundaries exist. A radar display image is projected onto a negative contrast reference map of the terrain to be navigated, the map and image having substantially the same scale and orientation. Means is provided in the path of the projected image to effect nutational movement between the map and display image. Motor means associated with the map serves to move the map in a plane transversely of the light path of the projected display image. Photocell means in back of the map is responsive to the light passing through the map from the projected image source. An electronic polarity switch is associated with the radar means for periodically reversing the contrast of the radar image and a similar electronic switch periodically inverts the output of the signal of the photocell means. Pulse-generating means, actuated periodically by the nutating means, simultaneously triggers the electronic switches so that the polarity of the output signal of the photocell means is inverted simultaneously with the reversing of the contrast of the radar display image. Means responsive to the output signal of the photocell means and associated electronic switch controls the motor means for maintaining alignment between the radar display image and the reference map.
In U. S. patent application Ser. No. 752,730, entitled, "An Apparatus For Establishing An In-Flight Position Of A Missile" which was filed Aug. 6, 1968, by Paul L. Brink, Jack L. Loser, and David M. Stutsman, there is disclosed a film drum scanner having a strip map attached to a drum which is rotatable at a constant angular velocity. The map is of a strip of land which is transverse to the direction of flight and over which a missile will fly on its flight to a target. When the missile passes over the ground which has previously been photographed, a lens system views or "sees" an area of ground, the image of which is projected through the end strip map to a photomultiplier detector. When the positive image of the ground scene comes into registration with the negative replica on the drum, a sharp decrease in the amount of light is passed through to the photo-multiplier detector. This signal is filtered and detected. By indexing the beginning of the replica and noting the position of the correlation function with respect to the indexing signal, the cross-track position of the missile at a known down-range position can be determined. When a fix position is made, a signal can be sent to an autopilot to correct the flight path of the missile so that the missile will be directed to its nominal flight path.